I got my hAP ax2 at home to learn Router OS 7 and also experiment with Wi-Fi 6/Wave2. It's been an interesting ride so far. Today I've been looking at the real world effects of placement of a router in a typical UK house - effect of thick stone walls, through floors, plasterboard walls etc.

Using the excellent Android Wi-Fi analyser, I factory reset the router so it was a pretty clean configuration and took screenshots of various signal strengths. This is me sat with my phone about 2m from the router, clear-ish line of sight:



I then restored the router back to it's day to day working configuration and noticed immediately that the signal strength lost ~10db, which is a reasonable amount:



Digging around I discovered that as per my normal configuration instructions, I'd set the country to UK. Never realised it made so much difference to transmit speed. On 5GHz it reduces the TX power from 26 down to 18.

I assume this is because of UK regulations? What units is TX power measured in?

I was also surprised to learn than the TX power varies depending upon the frequency. 5180GHz is 26 but 5260 is a little lower at 22. You live and learn! I also note that whilst you can reduce the TX power, you can't force it higher

What you observed is result of country-specific regulations, one of regulated thing is EIRP (which is Tx power + antenna gain). And limits indeed vary with frequency.

Power (both Tx and Rx) is shown in dBm ... that's logarithmic value, relative to 1mW (that's what the 'm' says). It's based on logarithm with base 10 and numbers are in "tenths" (that's what 'd' as 'deci' says). Being logarithmic, value 10dB means factor of 10, 20dB means factor of 100, -10dB means factor of 1/10 (or 0.1). Etc.

You can always check the regulatory limits, observed by ROS, by running command /interface/wifi/radio/reg-info country="United Kingdom" number=0 ... my Audience says that in lower part of 5GHz band (5170MHz-5330MHz) max allowed Tx power is 23dBm (200mW) while in upper part (5490MHz-5710MHz) allowed power is 30dBm (1000mW=1W) ... but comes with other strings attached. Mind that these values are EIRP.

Thanks for the reply, most enlightening. The reg-info command is very useful. Just gone through the various channels with country set to UK. Perplexed why I can't set to 5580/ax/Ceeee - console reports "no supported channels". This is frequency range 5570-5650 (channels 116-128). According to this Wiki article, this range should be okay in UK.

https://en.wikipedia.org/wiki/List_of_WLAN_channels

Remove "UK" country and this frequency works. This is the output of reg-info:

admin@ROUTER001] > /interface/wifi/radio/reg-info country="United Kingdom" number=0
ranges: 2402-2482/20
5170-5250/23/indoor
5250-5330/23/indoor/dfs
5490-5730/30/dfs
5735-5875/14

Just noticed that v7.13.1 has been released. I've just upgraded the TX powers have changed! The release notes says "wifi - use "Latvia" as default value for country" property". VERY weird that I happen to be looking at this when it changes... the power settings for default have dropped. I wonder what country is was defaulting to before tonight? Latvia seems to have the exact same regulations as UK.